rename PAYMENT_VARIANTS to PAYMENT_VARIANTS_API

[devkral]

fix issue #64
this should prevent credentials appearing in the log

[devkral]

patterns are
HIDDEN_SETTINGS = re.compile('API|TOKEN|KEY|SECRET|PASS|SIGNATURE', flags=re.IGNORECASE)

[codecov-io]

Codecov Report

Merging #137 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #137   +/-   ##
=======================================
  Coverage   79.13%   79.13%           
=======================================
  Files          27       27           
  Lines        1649     1649           
  Branches      190      190           
=======================================
  Hits         1305     1305           
  Misses        245      245           
  Partials       99       99

Impacted Files	Coverage Δ
payments/core.py	87.69% <100%> (ø)	⬆️

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[devkral]

hm, most probably some broken tests (django 1.11), I have fixed some in my branch:
payment_improvements
has some very disruptive changes so I won't create a pull request before being sure that everything works fine

[devkral]

now it should work

[devkral]

this change can save your keys if you have a bad day and enable debug in django.settings